Aluminium Pechiney

Aluminium Pechinay

Michel Garat

Willem Loue

Christian Pluchon

Marc Tavernier

Gerard Laslaz

Michel Brimont

Francois Coss&eacute;

This invention relates to a eutectic or hypereutectic aluminium-silicon alloy product suitable for thixoforming, comprising (by weight) 10 to 30% silicon and, if applicable, copper (<10%), magnesium (<3%), manganese (<2%), iron (<2%), nickel (<4%), cobalt (<3%) and other elements (<0.5% each and 1% in total), the microstructure of which is composed of primary silicon crystals, equiaxed type aluminium dendrites less than 4 mm in size and a eutectic composed of eutectic silicon grains and eutectic aluminium grains less than 4 mm in size.

Hypereutectic aluminium-silicon alloy product for semi-solid forming

A metal alloy mass of a defined porosity for forming in the semi-solid state. When the porosity is measured by cooling in ambient air from a temperature corresponding to a liquid fraction ratio between 30 and 70% to the ambient temperature, the mass has a porosity ratio, measured by image analysis, between 2 and 20%, and preferably between 3 and 8%. Alternatively, when the gassing level is measured by a solidification test under 80 hPa, the mass has a volumetric porosity ratio between 3 and 50% and preferably between 4 and 25%.

Metal alloy mass for forming in the semisolid state

The invention relates to an aluminum alloy for thixoforming with the composition (by weight): Si: 5%-7.2% Cu: 1%-5% Mg&lt;1% Zn&lt;3% Fe&lt;1.5% other elements&lt;1% each and&lt;3% in total, with % Si&lt;7.5-% Cu/3, which, when reheated to the semisolid state to the point at which a liquid fraction ratio between 35 and 55% is obtained, has an absence of non-remelted polyhedral silicon crystals.

Process for semi-solid forming of thixotropic aluminum-silicon-copper

Process for shaping metal materials in a semi-solid state

A pattern of an aluminum alloy article made from a foam of an organic substance. The pattern is immersed in a mold of dry sand containing no binder. The mold is filled with molten aluminum alloy from a feeder zone and the alloy is allowed to solidify, thereby creating at least one critical zone in which solidification takes place last. Before the solidified fraction of metal exceeds 40% by weight, an isostatic gas pressure is applied to the mold. The aluminum alloy has a solidification range higher than 30.degree. C. and a ratio R of the distance between the feeder zone and at least one critical zone to half the means thickness of the article over this distance is greater than 10. The isostatic gas pressure being applied is between 0.1 and 0.5 MPa.

Process for the lost foam casting, under low pressure, of aluminium

An improvement to the process for the lost-foam casting of metal articles. According to the process, the casting takes place under a controlled pressure which initially increases at a rate between 0.003 and 0.3 MPa for a first period of at most 5 seconds from the begining of the rise in pressure. The pressure then increases during a second period at a rate higher than the rate of increase during the first period, until the maximum desired pressure is attained.

Process for the lost-foam casting, under controlled pressure, of metal

An improvement in the lost foam casting process in which a foam pattern of a part to be cast is immersed in a dry sand mold and the mold is filled with molten metal in order to burn the pattern. According to the improvement, after filling but before the solidified fraction of metal exceeds 40% by weight, an isostatic gas pressure which increases at a predetermined and substantially constant rate to a predetermined maximum value is applied to the mold and maintained at the maximum value until solidification occurs. The rate of increase of pressure is determined as a function of the granulometry of the sand and depth of immersion of the pattern, to cause due to a temporary lag in pressure transmittal through the sand, a rapid and temporary overpressure of the molten metal relative to the sand at the sand/metal interface. The overpressure reaches a maximum value of 0.001 to 0.030 MPa at the beginning of the pressure application and declines as the applied pressure further increases. The invention is especially useful in the production of cast aluminum alloy parts having an improved level of compactness and a surface which is free from blowholes and carbon inclusions.

Process for lost foam casting of metal parts

An organic foam pattern of the article to be cast is immersed in a dry sand mold containing no binder, the mold is filled with molten aluminum or aluminum alloy which replaces the foam and gradually solidifies, and an increasing isostatic gas pressure is simultaneously applied to the mold and to the aluminum or aluminum alloy after filling of the mold is complete. The isostatic gas pressure rises to a maximum value higher than 1.5 MPa and up to 10 MPa, and results in cast articles having improved mechanical characteristics and, in particular, better resistance to fatigue.

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Saint Quentin sur Isere, France

Michel Garat